#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#include "highway.h"
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/rope>
#define mem(a,v) memset((a), (v), sizeof (a))
#define enl printf("\n")
#define case(t) printf("Case #%d: ", (t))
#define ni(n) scanf("%d", &(n))
#define nl(n) scanf("%I64d", &(n))
#define nai(a, n) for (int i = 0; i < (n); i++) ni(a[i])
#define nal(a, n) for (int i = 0; i < (n); i++) nl(a[i])
#define pri(n) printf("%d\n", (n))
#define prl(n) printf("%I64d\n", (n))
#define pii pair<int, int>
#define pil pair<int, long long>
#define pll pair<long long, long long>
#define vii vector<pii>
#define vil vector<pil>
#define vll vector<pll>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define mp make_pair
#define fi first
#define se second
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef cc_hash_table<int,int,hash<int>> ht;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> oset;
const double pi = acos(-1);
const int MOD = 1e9 + 7;
const int INF = 1e9 + 7;
const int MAXN = 130050;
const double eps = 1e-9;
vii adj[MAXN], all;
int n, m, vis[MAXN], dp[2][MAXN];
ll dist;
int solve(int root, int idx) {
deque<int> pq;
pq.pb(root);
vi edg, tmp(m, 1);
while (!pq.empty()) {
int u = pq.front(); pq.pop_front();
for (pii nx: adj[u]) {
if (dp[idx][nx.fi] != dp[idx][u] + 1) continue;
tmp[nx.se] = 0;
pq.pb(nx.fi);
if (dp[idx][nx.fi] < dp[idx^1][nx.fi])
edg.pb(nx.se);
}
}
reverse(edg.begin(), edg.end());
int lo = 0, hi = edg.size()-1, ans = -1;
while (lo <= hi) {
int mi = (lo+hi) / 2;
vi cur;
for (int i = 0; i <= mi; i++)
tmp[edg[i]] = 1;
ll w = ask(tmp);
if (w == dist)
lo = mi + 1;
else {
ans = mi;
hi = mi - 1;
}
for (int i = 0; i <= mi; i++)
tmp[edg[i]] = 0;
}
if (ans == -1)
return root;
pii ret = all[edg[ans]];
if (dp[idx][ret.fi] < dp[idx][ret.se])
swap(ret.fi, ret.se);
return ret.fi;
}
void find_pair(int N, vi U, vi V, int a, int b) {
n = N;
m = U.size();
for (int i = 0; i < m; i++) {
adj[U[i]].pb(mp(V[i],i));
adj[V[i]].pb(mp(U[i],i));
all.pb(mp(U[i], V[i]));
}
dist = ask(vi(m, 0));
int lo = 0, hi = m-1;
while (lo <= hi) {
int mi = (lo+hi) / 2;
vi tmp(m);
for (int i = 0; i <= mi; i++)
tmp[i] = 1;
ll w = ask(tmp);
if (w == dist)
lo = mi + 1;
else
hi = mi - 1;
}
int u = all[lo].fi, v = all[lo].se;
mem(vis, 0);
mem(dp, 0);
deque<int> pq;
vis[u] = 1; pq.pb(u);
while (!pq.empty()) {
int u2 = pq.front(); pq.pop_front();
for (pii nx: adj[u2]) {
if (vis[nx.fi]) continue;
vis[nx.fi] = 1;
dp[0][nx.fi] = dp[0][u2] + 1;
pq.pb(nx.fi);
}
}
mem(vis, 0);
vis[v] = 1; pq.pb(v);
while (!pq.empty()) {
int u2 = pq.front(); pq.pop_front();
for (pii nx: adj[u2]) {
if (vis[nx.fi]) continue;
vis[nx.fi] = 1;
dp[1][nx.fi] = dp[1][u2] + 1;
pq.pb(nx.fi);
}
}
int s = solve(u, 0);
int t = solve(v, 1);
answer(s, t);
}
